There’s a procedure used by SEO professionals called “keyword mapping”, by which they determine which pages on a website should be targeting each important search term. Now, it’s quite possible that you might decide to create new pages for each of the search terms you’re targeting. But the smarter website optimiser looks for opportunities to adapt and improve pages which already exist, as these will probably already have external links, as well as a “history” which Google will like.
How do you identify if you have any appropriate pages, and if so, which might be the best one? Simple. Search Google for pages on your website with the search term in question. See what it already has. The “search query modifier” you need to just return pages on your own site is “site:”.
Let’s say I wanted to analyse any existing pages on our website about the term “google ranking”. Here’s what I’d search for:
I see from this that there are already many pages on my site about the subject (no surprise there), but the one which Google chooses to show first is an article from two years ago. This might be a sensible page to use as a basis for one optimised to perform strongly in the Google results for the term “google ranking”.
Of course, if Google returns no results at all, you’ll have to start a new page. But see that as an opportunity!